Preparation of aromatic aldehydes by oxidation

ABSTRACT

A process for preparing aromatic aldehydes which process consists of oxidizing substituted or unsubstituted toluene, xylene, pseudocumene with a molecular oxygen-containing gas in the presence of 0.1 to 25 moles of nitrobenzene.

United States Patent Inventor Appl. No.

Ellis K. Fields Chicago, Ill.

Apr. 10, 1969 Sept. 28, 1971 Standard Oil Company Chicago, Ill.

Continuation-impart of application Ser. No. 597,869, Nov. 30, 1966, nowabandoned.

PREPARATION OF AROMATIC ALDEHYDES BY OXIDATION 3 Claims, No Drawings US.Cl

260/621 G, 260/346.2 M, 260/645, 260/623 R,

511 im. Cl C07c 47/52 [50] Field of Search. 260/621 G, 599

[56] References Cited UNITED STATES PATENTS 1,547,725 6/1923 Bibb v.260/621 1,909,354 5/1933 Jaeger. 260/599 1,909,355 5/1933 Jaeger 260/599Primary Examiner- Bernard Helfin Attorneys-Arthur G. Gilkes, William T.McClain and Gunar J. Blumberg ABSTRACT: A process for preparing aromaticaldehydes which process consists of oxidizing substituted orunsubstituted toluene, xylene, pseudocumene with a molecularoxygen-containing gas in the presence of Oil to 25 moles ofnitrobenzene.

PREPARATION OF AROMATIC ALDEHYDES BY OXIDATION This is acontinuation-in-part of Ser. No. 597,869 filed Nov. 30, 1966 and nowabandoned by the same inventor.

This invention relates to the oxidation of aromatics and particularlyrelates to the oxidation in the vapor phase, with molecularoxygemcontaining gas, aromatic compounds in the presence of one of thefollowing nitrocompounds; nitrobenzene, nitrotoluene, nitroxylene, or amixture of these to produce aromatic aldehydes.

The vapor-phase oxidation of aromatic compounds, more particularlymethylbenzenes, has been unattractive in the past because of lowconversions. in the prior an attempts at higher conversions have causedextensive oxidation of the aromatic compounds to carbon dioxide andwater. This is also true when oxidation is carried out in the presenceof metal and metal oxide catalysts.

l have discovered that aromatic compounds can be oxidized in the vaporphase with a molecular oxygen-containing gas in the presence ofnitrobenzene, nitrotoluene, nitroxylene or a mixture of these, to givegood yields of aromatic aldehydes.

For example, when toluene is oxidized in the vapor phase by air oroxygen in the presence of nitrobenzene good yields of benzaldehyde areobtained. Good yields of aromatic aldehydes are obtained when methylatedbenzenes and other aromatic compounds are oxidized according to myprocess. Substituted or unsubstituted toluenes, xylenes andpseudocumenes can be oxidized by the process of my invention.Representative compounds which can be oxidized include benzene, toluene,ortho-xylene, meta-xylene, para-xylene, pseudocumene, hemimellitene,mesitylene, durene, isodurene, prehnitene, pentamethylbenzene,naphthalene, land 2- methylnaphthalenes, dimethyl naphthalenes,acenaphthene, phenanthrene, anthracenes, pyrene, and other polycyclicaromatics; also all these aromatic compounds containing substituentssuch as fluoro, chloro, bromo, nitrile, carboxy, ester, anhydride andtrifluoromethyl groups. Examples of substituted aromatic compoundsinclude dimethyl isophthalate, dimethyl phthalate, phthalic anhydrideand benzotrifluoride.

In general, the process is carried out by oxidizing the aromaticcompounds in the vapor phase by airor oxygen-enriched air at about 0.1to 10 atmospheres pressure. The contact time can vary from about 0.1 to60 seconds. The temperature generally is maintained in the range of500650 C. and the reaction is carried out in the presence of 0.1 to molepercent of nitrobenzene, nitrotoluene, or nitroxylene. In the preferredprocess the air or molecular oxygen-containing gas is maintained at 1atmosphere pressure and a flow rate of 0.6 to 1 cubic foot per hour,giving a contact time of 2-15 seconds. The preferred temperature is550650 C. and the concentration of nitrobenzene is maintained at 1-7mole percent. The preferred aromatic hydrocarbons are toluene, xyleneand pseudocumene. My oxidation process can conveniently be run in areactor consisting of a tube of some inert material, preferably Vycor,quartz, or Pyrex andpvhich may be packed with beads or chips of the samematerial.

The aromatic aldehydes are useful as pesticides, as dyes, as chemicalintermediates, resins and plastics, antioxidants and pharmaceuticals.The aromatic aldehydes are particularly useful for preparing resins andplastics. They are also useful as pesticides and pharmaceuticals.

The following examples are included as illustrations of my process andare not intended as limitations thereof:

EXAMPLE l A solution of toluene (92 g., 1 mole) and nitrobenzene (1.23g., 0.0l moles) was passed through a Vycor tube filled with Vycor chipsat 600 C. with an airflow of 0,8 cubic feet per hour. The reaction timewas 7 hours 5 minutes with a contact time of 4.7 seconds. The reactionproducts were condensed in a series of three trops at dry-icetemperature. Distillation of the reaction mixture afforded 63.7 g.toluene and a residue of 23.7 g. The percent conversion of nitrobenzenewas 46 percent. Analysis of the residue by gas chromatography showed itto contain 9.81 g. toluene along with the following oxidation products:

EXAMPLE ll A solution of toluene (92 g., l mole) and nitrobenzene V(1.23 g., 0.01 moles) was passed through a Vycor tube filled ProductYield, mole l benzaldehyde l7.8 phenol 6.0 o-cresol 0.35

rn, p-cresol 4.6

Yields based on 8.5 percent conversion of toluene EXAMPLE Ill A solutionof toluene (92 g., 1 mole) and nitrobenzene (1.23 g., 0.01 moles) waspassed through a Vycor tube filled with Vycor chips at 650 C. with anairflow of 0.8 cubic feet per hour. The reaction time was 8 hours 10minutes with a contact time of 4.6 seconds. The reaction products werecondensed in a series of three trops at dry-ice temperature. Thereaction mixture was distilled to give 48.9 g. toluene and a residue of30.5 g. The percent conversion of nitrobenzene was percent. Gaschromatography analysis of the residue showed it to contain 133 g. oftoluene and the following oxidation products:

Product Yield, mole l benzaldehyde 1 L5 phenol 12.2 o-cresol L0 m,p-cresol 3.8

Yields based on 32 percent conversion of toluene.

EXAMPLE IV collected in a chilled receiver and the unreacted benzene wasdistilled to a pot temperature of l l3 C. The residue contained 6.085 g.of phenol and 0.605 g. of dibenzofuran. Dibenzofuran is fonned fromphenol at elevated temperatures.

EXAMPLE V To demonstrate clearly the effect of the nitrobenzene in thepractice of my invention, the oxidation of 1 mole of benzene wasrepeated exactly as in example IV, but the nitrobenzene was omitted. Thedistillation residue contained 1.41 g. of phenol and 0.0078 g. ofdibenzofuran: only about one-fifth as much phenol had formed in theabsence of nitrobenzene.

EXAMPLE VI EXAMPLE VIII The oxidation of benzene containing 2 molepercent of nitrobenzene was repeated as in example IV, using an airflowof 1.2 cubic feet per hour and a contact time of 3.3 seconds, to give4.8 g. of phenol and 0.76 g. of dibenzofuran.

EXAMPLE IX The oxidation of l mole of benzene was repeated exactly as inexample VIII, without nitrobenzene. No phenol was formed, and only atrace (less than 0.01 g.) of dibenzofuran.

EXAMPLE X To show that nitrobenzene formed in situ is also effective inthe oxidation of benzene to phenol, the oxidation of I mole of benzenecontaining 2 mole percent of 70 percent nitric acid was repeated as inexample VI, to give 3.26 g. of phenol and 0.5 g. of dibenzofuran.

EXAMPLE XI The oxidation of example X was repeated, using 4 mole percentof 70 percent nitric acid to give 4.34 g. of phenol and 0.66 g.ofdibenzofuran.

EXAMPLE XII At 400 C. the yield of phenol is appreciably reduced, asshown by repeating the oxidation of l mole of benzene as in example X,but at 400 C. to give 0.416 g. ofphenol and 0. l 36 g. of dibenzofuran.

EXAMPLE XIII Chlorobenzene, ll.7 mL, 1 mole, containing 5.035 ml. (0.05mole, 5 mole percent) of nitrobenzene, was oxidized at 600 C. with airat 0.6 cubic feet per hour over I minutes and a contact time of 6.0seconds to give 4.30 g. chlorophenol and 2.40 g. dichlorodibenzofuran.

EXAMPLE XIV The oxidation of 1 mole of chlorobenzene was repeatedexactly as in example XIII without nitrobenzene to give 1.5 g. ofchlorophenol and 0.45 g. of dichlorodibenzofuran.

EXAMPLE XV l-Chloronaphthalene, l62.6 ml., 1 mole, containing 10.27 ml.(0.l mole, 10 mole percent) was oxidized at 600 C. with air at 0.6 cubicfeet per hour, contact time 6.3 seconds, to give 4.1 g. chloronaphtholand 4.2 g. dichlorodinaphthofuran.

EXAMPLE XVI The oxidation of 1 mole of chloronaphthalene was repeatedexactly as in example XV to give 0.36 g. of chloronaphthol and 0.416 g.of dichlorodinaphthofuran.

EXAMPLE X VII A solution of 2.054 ml. (0.02 mole, 2 mole percent) ofnitrobenzene in I064 ml. (I mole) of toluene was oxidized at 600 C. withair at 0.3 cubic feet per hour over 342 minutes, contact time 9.8seconds, to give a mixture of benzaldehyde and cresols that analyzed:

benzaldehyde 3.0 g. o-cresol 2.6 g. mp-cresol 1.3 3.

EXAMPLE XVIII Oxidation of l mole of toluene exactly as in example XVIIwithout nitrobenzene gave a mixture that analyzed:

benzaldehyde 0.06 g. o-cresol 0.0l g. mp-cresol 0.0l 5.

EXAMPLE XIX Oxidation of 1 mole of o-xylene containing 2 mole percent ofnitrobenzene at 600 C. with air at 0.3 cubic feet per hour, contact time10.0 seconds, gave 4.8 g. of o-tolualdehyde and 2.0 g. of o-xylenol.

EXAMPLE XX Oxidation of 1 mole of o-xylene exactly as in example XIX,but without nitrobenzene gave 0.28 g. o-tolualdehyde and 0.46 g.o-xylenol.

EXAMPLE XXI Oxidation of 1 mole of m-xylene containing 2 mole percent ofnitrobenzene at 600 C. with air at 0.3 cubic feet per hour, contact time10.0 seconds, gave 3.2 g. of m-tolualdehyde and 3.8 g. of m-xylenol.

EXAMPLE XXII Oxidation of 1 mole of m-xylene as in example XXI, butwithout nitrobenzene gave 0.84 g. of m-tolualdehyde and 1.12 g. ofm-xylenol.

EXAMPLE XXIII Oxidation of I mole of p-xylene containing 2 mole percentof nitrobenzene at 600 C. with air at 0.3 cubic feet per hour, contacttime l0 seconds, gave 4.0 g. of p-tolualdehyde and 2.2 g. of p-xylenol.

EXAMPLE XXIV Oxidation of 1 mole of p-xylene as in example XXIII butwithout nitrobenzene gave 0.04 g. of p-tolualdehyde and 0.04 g. ofp-xylenol.

EXAMPLE XXV A solution of 1.027 ml. (0.01 mole, 2 mole percent) ofnitrobenzene in 69 ml. (0.5 mole) of pseudocumene was oxidized at 600 C.with air at 0.3 cubic feet per hour over 208 minutes, contact time 10seconds, to give 5.68 g. of dimethyl benzaldehyde and 1.08 g. oftrimethyl phenol.

EXAMPLE XXVI Oxidation of 0.5 mole of pseudocumene as in example XXVwithout nitrobenzene gave 0.86 g. of dimethyl benzaldehyde and 0. l 7 g.of trimethyl phenol.

EXAMPLE xxvn A solution of 5.135 ml. (0.05 mole, 5 mole percent) ofnitrobenzene in 92.9 ml. (1 mole) of fluorobenzene was oxidized at 600C. with air at 0.6 cubic feet per hour over 97 minutes, contact time 6.4seconds, to give 5.5 g. of fluorophenol and 0.22 g. ofdifluorodibenzofuran.

EXAMPLE XXVIll Oxidation of 1 mole of fluorobenzene as in example XXVll,but without nitrobenzene gave l.5 g. of fluorophenol and 0.09 g. ofdifluorodibenzofuran.

EXAMPLE XXIX EXAMPLE XXX Oxidation of 0.2 mole of methylbenzoate as inexample XXIX, but without nitrobenzene gave 0.197 g. of methylhydroxybenzoate and 0.287 g. of methyl dihydroxybenzoate.

I claim:

1. A process for preparing aromatic aldehydes which process comprisesoxidizing, with a molecular oxygen-containing gas, aromatic compoundsselected from the group consisting of substituted or unsubstitutedtoluene, xylene and pseudocumene in the presence of 0.1 to 25 molepercent nitrobenzene at a pressure of about 0.1 to 10 atmospheres andcontact times of about 0.1 to 60 seconds at an elevated temperature ofabout 500 to 650 C.

2. The process of claim 1 wherein the contact time is 2 to 15 secondsand the temperature is 550 to 650 C. and the concentration ofnitrobenzene is l to 7 mole percent.

3. The process for preparing benzaldehyde which process comprisesoxidizing toluene with a molecular oxygen-containing gas in the presenceof0.l to 25 mole percent nitrobenzene at a pressure of about 0.1 to l0atmospheres and contact times of about 0.1 to 60 seconds at an elevatedtemperature of about 500 to 600 C.

2. The process of claim 1 wherein the contact time is 2 to 15 secondsand the temperature is 550* to 650* C. and the concentration ofnitrobenzene is 1 to 7 mole percent.
 3. The process for preparingbenzaldehyde which process comprises oxidizing toluene with a molecularoxygen-containing Gas in the presence of 0.1 to 25 mole percentnitrobenzene at a pressure of about 0.1 to 10 atmospheres and contacttimes of about 0.1 to 60 seconds at an elevated temperature of about500* to 600* C.